As a method of reproducing two or more files that have been recorded on an optical disc while reading them in turn, a system that reads two files alternately and reproduces them by preparing a comparatively large buffer memory, reading a sufficient part of one file into the buffer memory, then reading the other file, and repeating these operations alternately has been proposed (in Patent Document 1, for example).    Patent Document 1: International Publication WO/2002/023896